The 157 nm technology on the basis of the F.sub.2 excimer laser proceeds from the development of the microlithographic projection illumination apparatus for using ever lower light wavelengths. This 157 nm technology has been under development for some time.
In the deep ultraviolet range, experience with suitable illuminating systems is already present with different components and functions which are also necessary for the 157 nm technology in order to illuminate a sufficiently large field homogeneously, telecentrically and with a selectable degree of coherence .sigma..
A problem associated therewith is that the availability of transmitting materials is greatly limited. Only CaF.sub.2 is already established as an optical material and is adequately permeable. Other fluorides are also known as being useable. However, attention has to be paid to minimalization of glass paths because the absorption is significantly higher compared to known deep ultraviolet systems and the resistance to radiation is reduced.